A walk behind pavement saw is a device typically used to cut through pavement slabs (i.e., concrete), and/or to cut grooves/slots in pavement surfaces. A typical pavement saw is very heavy, often weighing hundreds of pounds, and is made up of a rigid frame that supports a powerful engine which drives a rotary saw blade.
In one such prior art device, the frame rests on a set of front and rear wheels, with a pair of operator handles rigidly mounted to the rear of the frame so that an operator who stands behind the saw can see and operate such a device. The handles are usually bolted, welded, or otherwise fixed to the frame in a single position and are not readily adjustable to accommodate different size operators. In some prior art devices, the handles are “adjustable” in their connection with the frame because the position of the handles on the frame can be changed by manually loosening a wing nut, manually changing the pitch of the handles and then manually tightening the wing nut so as to return the device to a fixed position in a different desired position.
In such prior art devices, the saw blade is typically mounted near the front of the frame so that the cutting edge of the blade is in front of or just below the front of the frame. The height of the saw blade is typically above the pavement work surface and the depth of the cut is controlled by the operator lifting or lowering the handles so as to raise or lower the front end of the frame.
In one such standard prior art device, neither the front or rear wheels are configured or allowed to pivot. The reason for this is to prevent lateral movement of the saw blade when cutting. Unacceptable lateral movement of a spinning saw blade in the cut would likely result in a shattered saw blade which would pose a danger to the operator and others nearby. While this non-pivoting feature is desirable as a safety measure, it makes the movement or steering of such a device much more difficult.
In prior art pavement cutting saws, the rigid fixation of the handles of the device, to the frame of the device, cause the handles to travel in an arc as the front of the frame, which the saw blade is connected to, is raised and lowered. For example, raising the front of the frame pivots the handles downwardly (towards the pavement surface) behind the rear of the frame. If the diameter of the saw blade is large, the operator must often raise the front of the frame very high, thus pivoting the handles downwardly to the extent that at times the handles are about at the height of the operator's knees or lower. Due to the great weight of power pavement saws, lowering the handles to just above the pavement work surface makes the saw difficult to maneuver and exposes the operator to fatigue and/or the possibility of injury. Instead, in order to move the saw to and from the site of the cut, or to turn the saw, the operator must raise the front of the frame well above the pavement surface, high enough to completely disengage the saw blade from the cut. The operator can then push down on the handles to pivotally lift the front wheels off the pavement surface and pivot the machine around on its rear wheels to effectuate turning. Alternatively, the operator may lift up on the handle so as to effectuate a turn upon the front wheels of the device.
Accordingly, there is a need for a way to maintain the handles at a comfortable height above the pavement surface, largely independent of the height of the saw blade, particularly when the operator of the saw is turning or moving the machine with the saw blade raised above the pavement surface. It is an object of embodiments of the present invention to provide a pair of self leveling handles for use with a pavement saw or other similar machine, which enables the position of the handle bars to remain in the same general orientation and position regardless while the frame and blade of a device are lifted and lowered. Another object of embodiment of the present invention is to provide a mechanism wherein the handle height may be readily and quickly adjusted for operators of different heights, or even operator preferences.